Glazes are widely used to protect ceramic wares from contamination and provide beautiful appearance of the ceramic wares. In general, a glaze layer can be formed on a ceramic ware by applying a glaze thereon, and baking the applied glaze. Thus, since the glaze layer presents resistance to contamination and the beautiful appearance to the ceramic ware, it is being widely used in application areas of ceramic sanitary wares for toilets and bathrooms as well as general ceramic wares.
However, when the conventional glazes are used, there are problems that a yet-to-be dissolved substance easily remains in the glaze layer, or zirconium silicate of an emulsion agent is crystallized to appear on the outermost surface of the glaze layer. As a consequence, a beautiful, smooth surface with luster of the glaze layer can not be obtained.
In addition, there is a room for further improvement of the antifouling performance of the glaze layer. For example, to improve the antifouling performance, it is proposed to form a transparent glaze layer consisting of amorphous materials. In this case, the antifouling performance can be improved to some extent. However, it becomes difficult to provide the beautiful appearance of the glaze layer to articles because of the transparency of the glaze layer. Due to this reason, it will be necessary to form another glaze layer having a desired color between the transparent glaze layer and the ceramic ware. This two-layer structure leads to an increase in production time and cost.
In addition, in the case of using tin oxide or bone ash as the emulsion agent in conventional glazes for ceramic ware, there are problems that pore generation amount in the glaze layer after baking increases, and a beautiful semi-opaque glaze layer is not obtained by baking. For example, it is proposed to use a glaze having the composition of 80 wt % of SiO2; 6.5 wt % of Al2O3; 0.2 wt % of Fe2O3; 0.8 wt % of MgO; 8 wt % of CaO; 3 wt % of ZnO; 1 wt % of K2O; 0.5 wt % of NaO; 5 wt % of SnO2 (median diameter: 5 μm). However, this glaze is not melted even when baked at the temperature of 1200° C. In addition, there is a room of improvement in the antifouling performance and a degree of luster of the glaze layer.